The invention relates to a clamping apparatus for clamping off a hose in a fluid system for biological liquids, in particular blood.
Fluid systems for biological liquids typically comprise a pump apparatus for the fluid to be forwarded which is connected via hoses to a circulation or to other elements of the fluid system respectively. As an example for a fluid system of this kind, heart-lung machines may be named here, which are e.g. connected during a heart operation to the blood circulation of the patient in order to take over the functions of the heart and to maintain the blood circulation. In this it is very important that no air bubbles wherever possible are present in the blood which is forwarded into the circulation of the patient, since these represent a serious endangering of the patient. Therefore a bubble detector and a clamping apparatus are usually provided downstream from the pump in heart-lung machines. As soon as the bubble detector detects an air bubble, the clamping apparatus must clamp off the hose through which the forwarded blood flows into the body of the patient and thereby interrupt the blood supply to the patient as rapidly as possible in order that the air bubble can not penetrate into the body circulation of the patient. The clamping apparatus thus serves as an on/off switch for the flow connection between the blood pump and the body circulation of the patient. In order that the clamping apparatus can interrupt the flow connection sufficiently rapidly through clamping off the hose, it is desirable that its switching time amounts to less than 100 milliseconds, preferably at most 80 milliseconds.
Clamping apparatuses are known in which the clamping off takes place by means of a spindle and a step motor which drives the spindle. These apparatuses however have the disadvantage that they are constructionally complicated and expensive and that relatively large and powerful step motors are required for a sufficient speed. In addition, clamping apparatuses of this kind are self locking due to the spindle drive. In the event that the electrical system fails, it is therefore very difficult, if at all possible, to open or close the clamping apparatus manually.
Furthermore, clamping apparatuses are known in which the closing member which clamps off the blood conducting hose is electromagnetically actuated. The closing member is moved by means of an electromagnet, mainly against the force of a spring, into the closure position and is held there, or, on the contrary, is held in the open position against the force of a spring by an electromagnet. Through deactivation of the electromagnet the closing member then moves into the open position or into the closure position dependent of the specific design as a result of the spring force. Disadvantageous in clamping apparatuses of this kind is their high energy consumption, since energy is constantly required for at least one holding state, namely the holding of the closing member in the open position or the holding in the closure position, in order to supply the electromagnet with current. The constant current flow furthermore leads to a disadvantageous heat production. The high energy requirement is a considerable disadvantage in particular in portable or mobile systems respectively, since systems of this kind are usually supplied by batteries. Also in regard to situations in which the heart-lung machine can be operated only with emergency power it is desirable to keep the current requirement as low as possible. In addition, such electromagnetically operated clamping apparatuses also have the disadvantage that they can not be opened or closed manually when the electrical system fails.
Starting from this prior art, an object of the invention is therefore to propose a clamping apparatus for clamping off a hose in a fluid system for biological liquids which does not have these disadvantages. In particular the clamping apparatus should require as little energy (current) as possible during operation and be constructionally simple and as compact as possible. It should enable sufficiently rapid switching times of less than about 100 milliseconds and in addition be manually actuatable in a simple manner.
Thus in accordance with the invention a clamping apparatus for clamping off a hose in a fluid system for biological fluids, in particular blood, is proposed comprising a movably arranged closing member having a closing piece for clamping off the hose, comprising a permanent magnetic holding device which is arranged and designed in such a manner that it can hold the closing member against a force in two different stable equilibrium positions, namely an open position and a closing position, without it being necessary to supply energy to the permanent magnetic holding device for the holding in the respective equilibrium position, and comprising actuation means in order to move the closing member out of the open position into the closing position.
The permanent magnetic holding device is thus designed in such a manner that two stable equilibrium positions exist for the closing member, namely on the one hand an open position in which a hose which is laid in into the clamping apparatus is not or only slightly clamped so that the liquid can flow through the hose, and on the other hand a closure position in which the hose is clamped off through the closure position of the closing member so that no liquid can flow through the hose any longer. No energy in the form of current is required for holding the closing member in the two equilibrium positions. The closing member is held in the two equilibrium positions purely passively, namely permanent magnetically, which is a quite considerable advantage in regard to the energy consumption.
In addition no spindle drives or other self locking drives are required for the actuation of the clamping apparatus, for which reason the clamping apparatus is constructionally simple, very compact and in particular also manually actuatable, which means that it can be brought manually into the open position and into the closure position.
The actuation means preferably comprise at least one coil which is arranged in such a manner that it can exert an electromagnetic force on the closing member in the direction towards the closure position or in the direction towards the open position. Through activation of the coil, in addition to the permanent magnetic holding force, an electromagnetic force is produced which deflects the closing member out of its one stable equilibrium position to such an extent that it assumes its other equilibrium position. The coil need thus be actuated only if the closing member is to be brought from the open position into the closure position or conversely from the closure position into the open position.
In a preferred exemplary embodiment the closing member comprises two limbs and a transverse bar, with the limbs being connected to the transverse bar at a spacing from one another. The permanent magnetic holding device then comprises two permanent magnetic holders, each of which surrounds a limb in each case, and in which the closure piece is arranged at the transverse bar between the two limbs. Furthermore, for each limb of the closing member at least one coil which surrounds the limb for exerting an electromagnetic force on the limb is preferably provided. This exemplary embodiment is distinguished by its particularly reliable operating behavior.
Two separate coils are preferably provided as actuation means for the closing member or for each limb of the closing member, with a separate control and supply apparatus being provided in each case for each of the two separate coils. Through this measure an advantageous fault tolerance can be realized, which increases the operating reliability. If namely one of the two separate coils or one of the two control and supply apparatuses drops out as a result of a fault, for example through a break in a line or in a cable respectively or another defect, then the closing member can continue to be operated electromagnetically with the coil which is still fault free, so that the clamping apparatus remains completely capable of functioning.
A further advantageous measure consists in providing at least one spring element which acts on the closing member and which is arranged in such a manner that the spring force acts opposite to the magnetic force which the permanent magnetic holding device exerts on the closing member. Through this measure the clamping apparatus can be matched in a simple way to the properties of the respective hose which is used.
The clamping apparatus in accordance with the invention is in particular suitable for combining with a pump apparatus for forwarding a biological fluid, especially for combining with a blood pump, for example in a heart-lung machine.
Further advantageous measures and preferred embodiments of the invention result from the independent claims.